A heatpump system can be used to control the temperature of a certain medium such as, for example, the air inside of a building. A heatpump system generally comprises an evaporator, a condenser, a compressor and a series of lines (e.g., pipes, tubes, ducts) connecting these components together so that a refrigerant fluid can cycle therethrough. Typically, the evaporator is located adjacent to or within the medium (e.g., it is located inside the building) and the condenser is located remote from the medium (e.g., it is located outside of the building).
A heatpump system can operate in a first (forward) direction, wherein it cools the temperature-controlled environment, and a second (reverse) direction, wherein it heats the temperature-controlled environment. In the forward (i.e., cooling) direction, the evaporator is the heat-absorbing component (i.e., it absorbs heat from, and thus cools, the medium) and the condenser is the heat-rejecting component (i.e., it rejects the absorbed heat to the remote location). In the reverse (i.e., heating) direction, the evaporator is the heat-rejecting component and the condenser is the heat-absorbing component.
In a heatpump cycle, refrigerant fluid enters the heat-absorbing component as a low pressure and low-temperature vapor-liquid. As the vapor-liquid passes through the heat-absorbing component, it is boiled into a low pressure gas state. From the heat-absorbing component, the fluid passes through the compressor, which increases the pressure and temperature of the gas. From the compressor, the high pressure and high temperature gas passes through the heat-rejecting component whereat it is condensed to a liquid.
A heatpump system will often include an expansion valve immediately (or almost immediately) upstream of the heat-absorbing component. When the high pressure and high temperature liquid from heat-rejecting component passes through the expansion valve, the pressure of the fluid is reduced (e.g., the expansion valve throttles the fluid) and fluid is converted to a low pressure and low temperature vapor/liquid state. This low pressure and low temperature vapor/liquid is received by the heat-absorbing component to complete the cycle.
A heatpump cycle will often also include a distributor just downstream of the expansion valve. A distributor commonly includes a mixing compartment whereat fluid is evenly distributed to a plurality of tubes which feed the multiple circuits of the heat-absorbing component. A distributor can also include a flow restriction (e.g., a nozzle) upstream of its mixing compartment which increases the velocity of the fluid just prior to its entry into the mixing compartment to promote a turbulent mixing of liquid and vapor phases. For economic and/or envelope-size reasons, the distributor is often attached directly to the expansion valve to form an expansion-distribution assembly.
As was indicated above, when a heatpump system is operating in a first (i.e., forward and/or cooling) direction, the evaporator is the heat-absorbing component, and when it is operating in a second (i.e., reverse and/or heating) direction, the condenser is the heat-absorbing component. Thus, an expansion-distribution assembly may be positioned at the end of the evaporator which is its inlet when fluid travels in the first direction and/or may be positioned at the end of the condenser which is its inlet when fluid travels in the second direction.
When a heatpump system is operating in a direction corresponding to the expand-then-distribute direction, liquid (at a high pressure and high temperature) will pass through the expansion-distribution assembly and will be converted into a vapor/liquid (at a lower pressure and a lower temperature) for receipt by the heat-absorbing component. When the heatpump system is operating in the opposite direction, fluid passes “backwards” through the expansion-distribution assembly. An expansion-distribution assembly will typically include a gate mechanism (e.g., a check valve) to provide a throttle-bypassing passage when fluid travels backwards through the expansion chamber. Thus, the gate mechanism eliminates any premature and/or inefficient throttling of fluid in the expansion chamber during backward flow. However, the fluid must still travel backwards through the distribution chamber to reach the expansion chamber, and this backward flow of fluid through the distributor's velocity-increasing flow path can sometimes cause a relatively significant and, in any event, undesirable, pressure drop.